<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    const a = 10;
    const b = 2;
    const c = 5;

    let sum = a + b + c;

    console.log("Сумма: " + sum);
</script>
</body>
</html>